include(CMakePrintHelpers)

set(WITH_EXAMPLE_FOO foo)
set(WITH_EXAMPLE_BAR bar)
set(VARIABLES WITH_EXAMPLE_FOO WITH_EXAMPLE_BAR)

foreach(var ${VARIABLES})
    cmake_print_variables(${var})
    if(var MATCHES ^WITH_EXAMPLE_[a-zA-Z])
        message(STATUS "Found example : ${var}")
    endif()
endforeach()